In regard to a stabilized power supply circuit, such as a linear regulator and a switching regulator, that regulates an output voltage to a constant target value, it has been widely known to employ a phase compensation circuit to ensure stabilization of the power supply circuit. For example, such a technique is described in JP2003-058260A and JP2006-109421A, which corresponds to US 2007/0174017 A1. The phase compensation circuit is disposed between an internal node of an error amplifier that controls the output voltage and an output node that outputs the output voltage.
The phase compensation circuit described above requires a capacitive element (capacitor) having a withstand voltage corresponding to the output voltage. Therefore, it is necessary to increase the withstand voltage of the capacitive element with an increase in the target value of the output voltage.
In a general monolithic process, it is necessary to increase the thickness of an oxidized film between electrodes of the capacitive element so as to increase the withstand voltage. However, a capacitance value per unit area reduces with the increase in thickness of the oxidized film. Therefore, when the phase compensation circuit is integrated into a semiconductor integrated circuit (IC), a circuit area increases with the increase in the withstand voltage of the capacitive element. Also in a case where the capacitive element is provided by a discrete component, the size of the component increases with the increase in the withstand voltage. Therefore, a similar drawback arises.
To address the drawbacks described above, for example, JP2003-058260A and JP2006-109421A describe a technique to double an apparent capacitance value of the capacitive element of the phase compensation circuit by using an active element. However, such a technique requires an amplifier circuit having a frequency band equal to or greater than a frequency that appears as a capacity. Therefore, a circuit structure is complex, and consumption current increases.